The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Aspects of the present invention relate to an accumulating portal conveyor, comprising a drivable endless conveyor belt, a frame for supporting and guiding the conveyor belt, which frame is provided with a first helical path and a second helical path which lies at a distance from the first helical path, a bridging path and a return path, which are arranged such that under operating conditions the conveyor belt successively follows the first helical path upwardly, the bridging path, the second helical path downwardly and the return path, and such that in transverse direction of an upright plane through central centerlines of the first and second helical path a free passage below the bridging path and between the helical paths is provided.
A portal conveyor is known from WO 2014/073961. The known portal conveyor has a frame with two helical conveyor paths, a bridging path and a return path. A supply location is present at the lower side of the first helical path where articles are placed on a conveyor belt and a discharge location is present at the lower side of the second helical path where articles are removed from a conveyor belt. The free passage provides, for example, the possibility to allow another transport through the conveyor without obstructing the flow of articles in the portal conveyor. In some processes the supply speed of articles varies at the first helical path with respect to the discharge speed of articles at the second helical path. This problem can be solved with the known portal conveyor by applying separate conveyor belts at the helical paths and the bridging path and temporarily drive them at different speeds. However, a disadvantage thereof is that transfers between conveyor belts are present which may cause instability of the articles to be transported. This is particularly undesired in case of a portal conveyor, because its height makes managing of possible problems difficult.